Vehicle waste heat recovery system

ABSTRACT

A waste heat recovery system ( 100 ) for an engine ( 101 ) comprises a fluid supply ( 104 ); one or more evaporators ( 120, 121 ) adapted to transfer waste heat from the engine ( 101 ) to fluid from the fluid supply ( 104 ) to heat the fluid to a superheated vapor; a condenser ( 134 ); a bypass circuit ( 130 ) in fluid communication with an outlet on the one or more evaporators ( 120, 121 ) and an inlet on the condenser ( 134 ); and an injection port ( 465 ) in fluid communication with the fluid supply ( 104 ) and the bypass circuit ( 130 ) and adapted to inject fluid from the fluid supply ( 104 ) into the bypass circuit ( 130 ) to cool the superheated vapor in the bypass circuit ( 130 ). A waste heat recovery system ( 100 ) for an engine ( 101 ) also comprises one or more evaporators ( 120, 121 ) adapted to transfer waste heat from the engine ( 101 ) to fluid from a fluid supply ( 104 ) wherein the engine ( 101 ) generates the waste heat with the fluid.

TECHNICAL FIELD

The embodiments described below relate to, waste heat recovery systems,and more particularly, to a vehicle waste heat recovery system.

BACKGROUND OF THE INVENTION

Internal combustion (IC) engines are used throughout the world andmainly for motor vehicles. IC engines account for one of the largestconsumers of petroleum products known. Due to the large amount ofpetroleum products consumed by IC engines and the gases exhausted fromIC engines, numerous regulatory agencies have implemented regulations orare in the process of implementing regulations that require minimumaverage fuel economy of vehicles as well as limit the amount ofpollutants that are exhausted from vehicles.

Earlier attempts at reducing vehicle emissions have centered on exhaustgas treatments. For example, earlier attempts have introduced reagentsinto the exhaust gas stream prior to the gas passing through a catalystin order to effect selective catalytic reduction (SCR) of the nitrogenoxides (NO_(x)) in the exhaust gases. Additionally, many vehicles nowinclude exhaust gas recirculation (EGR) systems to recirculate at leastsome of the exhaust gases. Although EGR reduces the harmful emissions ofvehicles, it also often reduces the vehicle's fuel economy.

The uses of SCR and EGR have been effective in reducing the emissionproblems in the exhaust stream, but have done little in improving thefuel economy and fuel consumption of vehicles. With the tighterregulations that are being implemented, many manufacturers have turnedtheir focus to increasing the fuel economy of IC engines. It isgenerally known that only about thirty to forty percent of the energyproduced by the fuel combustion of IC engines translates to mechanicalpower. Much of the remaining energy is lost in the form of heat.Therefore, one particular area of focus in the motor vehicle industryhas been to recover some of the heat that is generated by the IC engineusing a Rankine cycle.

While these prior art attempts have improved the vehicle's efficiency,they lack adequate control of the working fluid and the working fluid'stemperature. For example, U.S. Pat. No. 4,031,705 discloses a heatrecovery system that heats the working fluid using heat from the ICengine's exhaust and the IC engine's cooling circuit, i.e., the ICengine's radiator. Therefore, while the '705 patent does utilizemultiple heat sources, there is no way to adequately control where theheat is being drawn from. This can be problematic at times sinceinsufficient flow of working fluid to a heat source can reduce theoverall efficiency of the heat recovery system and/or result in wetsteam being fed to the expander.

An additional problem with the '705 patent is that the bypass circuitdirects vapor directly into a condenser. Although this is typically nota problem for lower temperature and/or pressure vapors, as thetemperature and/or pressure increases, the shock to the condenser causedby receiving superheated vapor can reduce the life expectancy of thecondenser.

The embodiments described below overcome these and other problems and anadvance in the art is achieved. The embodiments described below disclosea waste heat recovery system for an engine that includes a valve moduleto selectively control the flow of a working fluid between two or moreevaporators. Further, the embodiments described below can include abypass system that can cool superheated working fluid prior to reachinga condenser to alleviate and reduce some of the thermal shockexperienced by the condenser.

SUMMARY OF THE INVENTION

A waste heat recovery system for an engine is provided according to anembodiment. The waste heat recovery system comprises a fluid supply andtwo or more evaporators positioned in parallel to one another andreceiving waste heat from the engine. According to an embodiment, thewaste heat recovery system further comprises a valve module including aninlet port in fluid communication with the fluid supply, a first outletport in fluid communication with a first evaporator of the two or moreevaporators, and a second outlet port in fluid communication with asecond evaporator of the two or more evaporators for selectivelyproviding a fluid communication path between the fluid supply and one ormore of the two or more evaporators. According to an embodiment, anexpander is in fluid communication with an outlet of the two or moreevaporators and a condenser is in fluid communication with an outlet ofthe expander and an inlet of the fluid supply.

A waste heat recovery system for an engine is provided according toanother embodiment. The waste heat recovery system comprises a fluidsupply and one or more evaporators in fluid communication with the fluidsupply and receiving waste heat from the engine. According to anembodiment, the waste heat recovery system also includes a bypass valve.The bypass valve includes an inlet port in fluid communication with anoutlet of the one or more evaporators. The bypass valve further includesa first outlet port in fluid communication with an expander and a secondoutlet port in fluid communication with a condenser, wherein the secondoutlet port includes an injection port in fluid communication with thefluid supply.

A waste heat recovery system for an engine is provided according to anembodiment. The waste heat recovery system comprises one or moreevaporators adapted to transfer waste heat from the engine to fluid froma fluid supply wherein the engine generates the waste heat with thefluid.

A waste heat recovery system for an engine is provided according to anembodiment. The waste heat recovery system comprises one or moreevaporators adapted to transfer waste heat from the engine to fluid froma fluid supply to heat the fluid to a superheated vapor. The waste heatrecovery system includes a bypass circuit in fluid communication withthe outlet on the one or more evaporators and an inlet on a condenser.The waste heat recovery system further includes an injection port influid communication with the fluid supply and the bypass circuit whereinthe fluid from the fluid supply cools the superheated vapor in thebypass circuit based on a parameter in the waste heat recovery system orthe engine.

A method for recovering waste heat from an engine is provided accordingto an embodiment. The method comprises a step of selectively providing afluid from a fluid supply to two or more evaporators positioned inparallel, which receive waste heat from the engine. According to anembodiment, the method further comprises a step of outputting the fluidfrom one or more of the two or more evaporators to an expander, whichconverts at least a portion of the energy of the fluid into mechanicalenergy. According to an embodiment, the method further comprises a stepof outputting the fluid from the expander to a condenser in fluidcommunication with the fluid supply.

A method of recovering waste heat from an engine is provided accordingto an embodiment. The method comprises generating the waste heat withthe engine from fluid from a fluid supply and transferring waste heatfrom the engine to fluid from the fluid supply with one or moreevaporators.

A method of recovering waste heat from an engine with a waste heatrecovery system comprises generating superheated vapor with one or moreevaporators with the waste heat from the engine and cooling thesuperheated vapor with fluid from a fluid supply based on a parameter inthe waste heat recovery system or the engine.

ASPECTS

According to an aspect, a waste heat recovery system for an enginecomprises:

-   -   a fluid supply;    -   two or more evaporators positioned in parallel to one another        and receiving waste heat from the engine;    -   a valve module including an inlet port in fluid communication        with the fluid supply, a first outlet port in fluid        communication with a first evaporator of the two or more        evaporators, and a second outlet port in fluid communication        with a second evaporator of the two or more evaporators for        selectively providing a fluid communication path between the        fluid supply and one or more of the two or more evaporators;    -   an expander in fluid communication with an outlet of the two or        more evaporators; and    -   a condenser in fluid communication with an outlet of the        expander and an inlet of the fluid supply.

Preferably, the valve module comprises a first liquid control valveselectively providing a fluid communication path between the fluidsupply and the first evaporator and a second liquid control valveselectively providing a fluid communication path between the fluidsupply and the second evaporator.

Preferably, the first and second liquid control valves compriseproportional valves.

Preferably, the first and second liquid control valves compriseproportional needle valves.

Preferably, the waste heat recovery system further comprises one or morebushings positioned within a housing of the valve module and forming asubstantially fluid-tight seal with a valve member of the proportionalneedle valve.

Preferably, the valve member comprises a tapered needle having a maximumdiameter, which tapers down to a minimum diameter.

Preferably, the waste heat recovery system further comprises anelastomer sealing member forming a substantially fluid-tight sealbetween the valve member and the housing outside of the substantiallyfluid-tight seal between the valve member and the one or more bushings.

Preferably, the waste heat recovery system further comprises a pressurecontrol valve in parallel with the valve module.

Preferably, the waste heat recovery system further comprises a vaporcontrol module positioned between the two or more evaporators and theexpander for selectively providing a fluid communication path betweenthe two or more evaporators and the expander or the two or moreevaporators and a bypass circuit.

Preferably, the vapor control module comprises a bypass valve comprisingan inlet port in fluid communication with the two or more evaporators, asecond fluid port in fluid communication with the bypass circuit andselectively in fluid communication with the inlet port, and a thirdfluid port in fluid communication with the expander and selectively influid communication with the inlet port.

Preferably, the bypass valve comprises a pilot valve actuator foractuating the bypass valve from a first position to a second position.

Preferably, the pilot valve actuator is selectively in fluidcommunication with the fluid supply via a pilot supply valve.

Preferably, the waste heat recovery system further comprises aninjection port in fluid communication with the second fluid port andselectively in fluid communication with the fluid supply via ade-superheat control valve.

Preferably, the waste heat recovery system further comprises a venturipositioned in the second fluid port.

According to another aspect, a waste heat recovery system for an enginecomprises:

-   -   a fluid supply;    -   one or more evaporators in fluid communication with the fluid        supply and receiving waste heat from the engine;    -   a bypass valve including:        -   an inlet port in fluid communication with an outlet of the            one or more evaporators;        -   a first outlet port in fluid communication with an expander;            and        -   a second outlet port in fluid communication with a            condenser, wherein the second outlet port includes an            injection port in fluid communication with the fluid supply.

Preferably, the waste heat recovery system further comprises:

-   -   two or more evaporators positioned in parallel to one another;        and    -   a valve module including an inlet port in fluid communication        with the fluid supply, a first outlet port in fluid        communication with a first evaporator of the two or more        evaporators, and a second outlet port in fluid communication        with a second evaporator of the two or more evaporators for        selectively providing a fluid communication path between the        fluid supply and one or more of the two or more evaporators.

Preferably, the valve module comprises a first liquid control valveselectively providing a fluid communication path between the fluidsupply and the first evaporator and a second liquid control valveselectively providing a fluid communication path between the fluidsupply and the second evaporator.

Preferably, the first and second liquid control valves compriseproportional valves.

Preferably, the first and second liquid control valves compriseproportional needle valves.

Preferably, the waste heat recovery system further comprises one or morebushings positioned within a housing of the valve module and forming asubstantially fluid-tight seal with a valve member of the proportionalneedle valve.

Preferably, the valve member comprises a tapered needle having a maximumdiameter, which tapers down to a minimum diameter.

Preferably, the waste heat recovery system further comprises anelastomer sealing member forming a substantially fluid-tight sealbetween the valve member and the housing outside of the substantiallyfluid-tight seal between the valve member and the one or more bushings.

Preferably, the waste heat recovery system further comprises a pressurecontrol valve in parallel with the valve module.

Preferably, the bypass valve comprises a pilot valve actuator foractuating the bypass valve from a first position to a second position.

Preferably, the pilot valve actuator is selectively in fluidcommunication with the fluid supply via a pilot supply valve.

Preferably, the waste heat recovery system further comprises a venturipositioned in the second fluid port.

-   According to an aspect, waste heat recovery system for an engine,    comprises:    -   one or more evaporators adapted to transfer waste heat from the        engine to fluid from a fluid supply wherein the engine generates        the waste heat with the fluid.

Preferably, the engine is in fluid communication with the fluid supply.

Preferably, the fluid supply comprises a fuel tank for the engine.

Preferably, the fluid comprises fuel for the engine.

-   According to an aspect, a waste heat recovery system for an engine,    comprising:    -   one or more evaporators adapted to transfer waste heat from the        engine to fluid from a fluid supply to heat the fluid to a        superheated vapor;    -   a bypass circuit in fluid communication with the outlet on the        one or more evaporators and an inlet on a condenser; and    -   an injection port in fluid communication with the fluid supply        and the bypass circuit wherein the fluid from the fluid supply        cools the superheated vapor in the bypass circuit based on a        parameter in the waste heat recovery system or the engine.

Preferably, the parameter is a temperature in the waste heat recoverysystem.

Preferably, the parameter is a pressure in the waste heat recoverysystem.

Preferably, the parameter is a power output of the engine.

Preferably, the parameter is a parameter of a vapor control module.

According to another aspect, a method for recovering waste heat from anengine comprises:

-   -   selectively providing a fluid from a fluid supply to two or more        evaporators positioned in parallel, which receive waste heat        from the engine;    -   outputting the fluid from one or more of the two or more        evaporators to an expander, which converts at least a portion of        the energy of the fluid into mechanical energy; and    -   outputting the fluid from the expander to a condenser in fluid        communication with the fluid supply.

Preferably, the step of selectively providing the fluid from the fluidsupply to the two or more evaporators comprises proportionallycontrolling a fluid communication path between the fluid supply and afirst one of the two or more evaporators with a first liquid controlvalve and proportionally controlling a fluid communication path betweenthe fluid supply and a second one of the two or more evaporators with asecond liquid control valve.

Preferably, the proportional control uses a needle shaped valve memberthat forms a substantially fluid-tight seal with one or more bushings.

Preferably, the method further comprises a step of actuating a pressurecontrol valve to control a pressure of the fluid provided to the two ormore evaporators.

Preferably, the step of outputting the fluid from the two or moreevaporators to the expander comprises using a bypass valve including afluid inlet port in fluid communication with the two or moreevaporators, a first outlet port in fluid communication with theexpander, and a second outlet port in fluid communication with thecondenser.

Preferably, the method further comprises a step of actuating the bypassvalve to a first position to open a fluid communication path between thefluid inlet port and the second outlet port.

Preferably, the method further comprises a step of injecting the fluidfrom the fluid supply into the second outlet port.

Preferably, the method further comprises a step of actuating the bypassvalve to a second position to open a fluid communication path betweenthe fluid inlet port and the first outlet port by opening a fluidcommunication path between the fluid supply and a pilot valve actuatorof the bypass valve.

According to another aspect, a method of recovering waste heat from anengine, comprises:

generating the waste heat with the engine from fluid from a fluidsupply; and

transferring waste heat from the engine to fluid from the fluid supplywith one or more evaporators.

Preferably, the fluid is a fuel for the engine.

Such an arrangement offers the convenience of a single fluid for bothheat generation and heat transfer purposes. It also offers a convenientmechanism for disposal of working fluid where a working fluid is proneto breaking down.

According to another aspect, a method of recovering waste heat from anengine with a waste heat recovery system, comprises:

-   -   generating superheated vapor with one or more evaporators with        the waste heat from the engine; and    -   cooling the superheated vapor with fluid from a fluid supply        based on a parameter in the waste heat recovery system or the        engine.

Preferably, the parameter is a temperature in the waste heat recoverysystem.

Preferably, the parameter is a power output of the engine.

Preferably, the parameter is a parameter of a vapor control module.

In each of the foregoing aspects, the engine may be an internalcombustion engine.

Preferably, the internal combustion engine is a reciprocating pistonengine.

Preferably, the internal combustion engine is configured to be mountedon, and to drive, a vehicle.

Preferably, the internal combustion engine is configured to operateaccording to a highway cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic of a waste heat recovery system for an engineaccording to an embodiment.

FIG. 2 shows a cross-sectional view of a valve module according to anembodiment.

FIG. 3 shows a cross-sectional view of a portion of a liquid controlvalve according to an embodiment.

FIG. 4 shows a cross-sectional view of a vapor control module accordingto an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-4 and the following description depict specific examples toteach those skilled in the art how to make and use the best mode ofembodiments of a vehicle waste heat recovery system. For the purpose ofteaching inventive principles, some conventional aspects have beensimplified or omitted. Those skilled in the art will appreciatevariations from these examples that fall within the scope of the presentdescription. Those skilled in the art will appreciate that the featuresdescribed below can be combined in various ways to form multiplevariations of the vehicle waste heat recovery system. As a result, theembodiments described below are not limited to the specific examplesdescribed below, but only by the claims and their equivalents.

FIG. 1 shows a schematic of a waste heat recovery system 100 for anengine 101 according to an embodiment. The waste heat recovery system100 may be implemented for an engine 101 of a motor vehicle (not shown),for example. Therefore, the engine 101 may comprise an IC engine, inparticular a reciprocating piston engine. The vehicle may be an on-roadtruck, the operation of which is set out in the standard ‘highway cycle’or World Harmonised Test Cycle (WHTC). Such a truck engine mayparticularly be powered by diesel or natural gas. According to anembodiment, the waste heat recovery system 100 can include a liquidcontrol module 102 and a steam control module 103. According to anembodiment, the waste heat recovery system 100 includes a fluid supply104. The fluid supply 104 may include a fluid, such as water, Freon®,ethanol, etc. The particular fluid used may vary from one application toanother. For example, the fluid may be the fuel used by the engine 101.

A high-pressure fluid pump 105 is in fluid communication with an outletof the fluid supply 104. The high-pressure fluid pump 105 may be drivenby the engine 101 or may be driven by a separate electric motor, forexample. The high-pressure fluid pump 105 can elevate the pressure ofthe fluid from a reservoir pressure to a higher threshold pressure. Insome embodiments, the high-pressure fluid pump 105 may raise thepressure of the fluid to a threshold pressure of approximately 40 bar(580 psi) from the reservoir pressure, which is typically at atmosphericpressure. However, other threshold pressures are certainly possible andthe particular example pressure should in no way limit the scope of thepresent embodiment. At the outlet of the high-pressure fluid pump 105,are optional temperature 106 and pressure 107 sensors. The temperatureand pressure sensors 106, 107 are in fluid communication with thehigh-pressure fluid pump 105 via a fluid line 108.

According to an embodiment, the fluid line 108 can be in fluidcommunication with a plurality of other fluid lines via a line manifold109, which are shown in FIG. 1 and will be described from left to rightas shown in FIG. 1. According to an embodiment, the waste heat recoverysystem 100 can include a pressure control valve 110, which is in fluidcommunication with the line manifold 109 via a fluid line 111. The fluidline 111 branches off from the fluid line 108. The pressure controlvalve 110 can control the fluid pressure within the liquid controlmodule 102 to ensure that the high-pressure fluid pump 105 does notover-pressurize the fluid in the liquid control module 102. In manyembodiments, the high-pressure fluid pump 105 can pressurize the fluidto a higher pressure than is desired to be delivered to the rest of thesystem 100. Therefore, the pressure control valve 110 can regulate thefluid pressure in the liquid control module 102 so it does not exceed athreshold pressure. The pressure control valve 110 is further in fluidcommunication with the fluid supply 104 via a fluid line 112. Accordingto an embodiment, the pressure control valve 110 may be controlled basedon a predetermined set point pressure or may be actively controlled by amain system controller (not shown).

The main system controller and the electrical leads to the controllablecomponents of the waste heat recovery system 100 are not shown in FIG. 1to reduce the complexity of the figure. However, those skilled in theart will readily appreciate suitable electronics that may be used tocontrol the waste heat recovery system 100. For example, the main systemcontroller may comprise a portion of the vehicle's main electronics.Those skilled in the art can readily appreciate that the electronics cancontrol the various valves that are described further below based ontemperature and pressure measurements of the system, for example. Solong as the electronics can adequately control the actuation of thevarious valves discussed below, the particular electronics used is notimportant for purposes of the claims that follow and thus, should in noway limit the scope of the presently described embodiment.

According to an embodiment, the waste heat recovery system 100 canfurther include a system drain valve 113. In the embodiment shown, thesystem drain valve 113 comprises a normally open solenoid actuatedvalve; however, other types of valves can certainly be used. Whende-actuated, the system drain valve 113 can drain the fluid back to thefluid supply 104. This may occur when the vehicle is turned off, whenfluid is not desired to be run through the waste heat recovery system100, or in the event of an emergency, for example.

Moving to the right in FIG. 1, the waste heat recovery system 100further comprises a valve module 114. According to an embodiment, thevalve module 114 can be in parallel with the pressure control valve 110.Therefore, those skilled in the art can readily recognize that while thehigh-pressure fluid pump 105 may deliver a varying pressure that ishigher than the desired threshold pressure to the liquid control module102, the pressure control valve 110 can ensure that the valve module 114receives a relatively constant input pressure. The valve module 114 caninclude one or more fluid inlets 115 and two or more fluid outlets 116,117. In the embodiment shown, only one fluid inlet 115 is shown.However, in other embodiments, the fluid line 108 may branch off beforereaching the valve module 114, and thus, the valve module 114 caninclude more than one fluid inlet. According to an embodiment, the valvemodule 114 can include two or more liquid control valves 118, 119. Inone embodiment, the two or more liquid control valves 118, 119 can be inthe form of proportional valves.

According to an embodiment, the valves 118, 119 may compriseproportional needle valves (See FIGS. 2 & 3); however, those skilled inthe art will readily recognize other types of valves may be utilized.The proportional needle valves are described in more detail below.According to an embodiment, the valve module 114 can selectively providea fluid communication path between the fluid supply 104 and one or moreof the two or more evaporators 120, 121.

According to an embodiment, the two or more evaporators 120, 121 mayreceive waste heat generated by the engine 101. For example, in oneembodiment, the first evaporator 120 uses the heat from the engine's EGRwhile the second evaporator 121 uses the heat from the engine's exhaust.A third evaporator, not shown, may receive heat from a third source,such as the charge air circuit. According to an embodiment, the two ormore evaporators 120, 121 may be at different temperatures. Therefore,the valve module 114 can control the actuation of the valves 118, 119based on a measured temperature at the inlet of the vapor control module103. In addition to the temperature measured at the inlet of the vaporcontrol module 103, pressure sensors 122, 123 may be provided at theoutlets 116, 117 of the valve module 114. It should be appreciatedhowever, that the pressure sensors 122, 123 are optional and may beomitted.

Because of the elevated temperature of the two or more evaporators 120,121, the liquid leaving the valve module 114 can become a superheatedvapor. For example, in one embodiment, the valve module 114 can controlthe two or more valves 118, 119 such that the superheated vapor enteringthe vapor control module 103 is at approximately 400° C. (752° F.) and40 bar (580 psi). However, those skilled in the art can readilyappreciate that these values may vary based on the particularapplication and should in no way limit the scope of the presentembodiment.

According to the embodiment shown, the two evaporators 120, 121 are influid communication with the vapor control module 103 via fluid lines125, 126, which join prior to an inlet port 127 of the vapor controlmodule 103. A cross-sectional view of the vapor control module 103 isshown in greater detail in FIG. 4 and discussed further below. Withregard to the schematic shown in FIG. 1, it can be seen that the vaporcontrol module 103 can comprise a bypass valve 128. In the embodimentshown, the bypass valve 128 comprises a spring biased, fluid actuated3/2-way valve. However, those skilled in the art can readily appreciatealternative valve designs that will fall within the scope of the claimsthat follow.

In the embodiment shown, the bypass valve 128 can selectively provide afluid communication path between the two or more evaporators 120, 121and either an expander 129 or a bypass circuit 130. According to anembodiment, the bypass valve 128 can include the inlet port 127, a firstoutlet port 157, and a second outlet port 158. According to anembodiment, the bypass valve 128 can be biased towards a first positionwhere a fluid communication path is provided between the two or moreevaporators 120, 121 and the bypass circuit 130. Therefore, in a defaultposition, the expander 129 is bypassed and waste heat from the engine101 is not recovered and rather, flows directly to a condenser 134.According to an embodiment, in the first position, the fluid from thetwo or more evaporators 120, 121 flows through a needle valve 131 and aventuri 132. In some embodiments, the venturi 132 can receive anoptional fluid supply from the liquid control module 102 via ade-superheat control valve 133. Valve 133 is in fluid communication withthe fluid line 108 and thus, the fluid supply 104. As can beappreciated, the fluid within the fluid line 108 is pressurized to thethreshold pressure, but is not heated yet by the evaporators 120, 121.Therefore, injection of fluid from the fluid supply 104 can cool thesuperheated vapor flowing through the vapor control module 103 tode-superheat the fluid. As can be seen, the bypass circuit 130 is influid communication with the condenser 134 via a fluid line 135.Therefore, by injecting the superheated vapor with fluid from the fluidsupply 104 and thus, de-superheating the fluid, a substantially coolerfluid can be provided to the condenser 134, which reduces the thermalshock to the condenser 134. The fluid can flow from the condenser 134back to the fluid supply 104 via a low-pressure pump 135 positioned inthe fluid line 136.

According to an embodiment, actuating a pilot supply valve 137 and anexhaust valve 138 can actuate the bypass valve 128 from the firstposition to a second position. The pilot supply valve 137 can supplyfluid from the fluid supply 104 to a pilot valve actuator 139 via thefluid line 140. Therefore, the pilot supply valve 137 can selectivelyprovide a fluid communication path between the fluid supply 104 and thepilot valve actuator 139. The fluid supplied to the pilot valve actuator139 can actuate the bypass valve 128 to a second position. According toan embodiment, in the second position, the bypass valve 128 canselectively provide a fluid communication path between the two or moreevaporators 120, 121 and the expander 129. The superheated vapor flowsto the expander 129 where it reduces in enthalpy while expanding as isgenerally known in the art. Therefore, the expander 129 can convert atleast some of the energy of the superheated vapor to mechanical work.The expander 129 can comprise a variety of well-known devices, such as aturbine, a piston, a vapor engine, such as a rotary vane type vaporengine, etc. The particular type of expander 129 utilized is notimportant for purposes of the present description and should in no waylimit the scope of the claims that follow. For purposes of the presentapplication, the important aspect of the expander 129 is that it canconvert some or a portion of the energy of the superheated vapor intouseful mechanical energy. In some embodiments where the expander 129comprises a vapor engine, for example, the expander 129 can be coupledto the crankshaft or other suitable component of the engine 101 in orderto add power to the engine 101 as is generally known in the art.Therefore, in times when the expander 129 is not generating usefulpower, the engine 101 does not transfer power to the expander 129, whichwould decrease the engine's efficiency.

According to an embodiment, the fluid can leave the expander 129 andtravel to the condenser 134 via the fluid line 135 where the fluid iscooled and delivered back to the fluid supply 104.

With a basic description of the overall waste heat recovery system 100,attention is now drawn to particular features of the waste heat recoverysystem 100 that allow for accurate fluid control and high temperatureand pressure operation.

FIG. 2 shows a cross-sectional view of the valve module 114 according toan embodiment. According to an embodiment, the valve module 114comprises a housing 214, which may be separated into multiple parts asshown. According to the embodiment shown, the valve module 114 comprisesthe two liquid control valves 118, 119. According to an embodiment, thefirst liquid control valve 118 comprises a normally opened valve whilethe second liquid control valve 119 comprises a normally closed valve.

According to an embodiment, the first liquid control valve 118 comprisesa biasing member 244, which biases a valve member 245 away from a valveseat 246. In the embodiment shown, the valve member 245 also comprises aneedle. A linear stepper motor 247 or some other actuator can beprovided to actuate the valve member 245 towards the valve seat 246.According to an embodiment, the second liquid control valve 119comprises a biasing member 240, which biases a valve member 241 towardsa valve seat 242. In the embodiment shown, the valve member 241comprises a movable needle. The needle is tapered, which allows forproportional control of the fluid. A linear stepper motor 243 or someother actuator can be provided to actuate the valve member 241 away fromthe valve seat 242.

Although other types of actuators are certainly possible, linear steppermotors are generally known and can provide relatively accuratepositional control, which can allow proportional fluid control.Therefore linear stepper motors are particularly suitable for thepresent application.

It should be appreciated that while the liquid control valves 118, 119are described as comprising normally open and normally closed valves,the reverse could also occur. Alternatively, both of the valves 118, 119may be biased towards the same direction, i.e., both normally closed orboth normally open. Therefore, the particular configuration shown shouldin no way limit the scope of the present embodiment.

As shown in FIG. 2, the valve member 241 can selectively provide a fluidcommunication path between the inlet 115 and the outlet 117. Similarly,the valve member 245 can selectively provide a fluid communication pathbetween the inlet 115 and the outlet 116.

FIG. 3 shows an enlarged view of a portion of the valve 118 according toan embodiment. Although the discussion relates to the valve 118, itshould be appreciated that other than the position of the biasingmembers 240, 244, the valves operate substantially similarly. Therefore,the features discussed in relation to FIG. 3 can easily be applied forthe valve 119. As mentioned above, the waste heat recovery system 100can operate under relatively high pressures (40 bar, 580 psi) andelevated temperatures. Therefore, the valves 118, 119 include certainfeatures that allow for such high pressures without failing prematurely.According to an embodiment, the valve seat 246 can comprise one or morebushings 346, which forms a substantially fluid tight seal with thevalve module housing 214. In the embodiment shown, a one-piece bushing346 is provided; however, it should be appreciated that in alternativeembodiments, the bushing 346 can be separated into multiple components.The bushing 346 can form a fluid tight seal with the housing 214 via oneor more sealing members 360, 361, 362.

According to an embodiment, the bushing 346 can comprise a lower bore347 and an upper bore 348. The valve member 245 can slide within thelower and upper bores 347, 348 and can form a substantially fluid-tightseal. The seal between the valve member 245 and the bores 347, 348 isdue to the extremely tight tolerances between the components. Althoughthe particular dimensions may vary, in one embodiment, the differencebetween the inner radius of the bores 347, 348 and the outer radius ofthe valve member 245 is between 5-10 microns (0.0002-0.0004 inches). Forexample, in one embodiment, the valve member 245 comprises a maximumdiameter, D₁ of 2.0000 mm while the bores 347, 348 comprise an innerdiameter of 2.0005 mm.

According to the embodiment shown, the valve member 245 is in the closedposition wherein a portion of the valve member 245 having a maximumdiameter, D₁ is sealed against the lower bore 347. Consequently, becauseof the tight sealing tolerance, a substantially fluid-tight seal isformed and most of the fluid is prevented from flowing from the inlet115 towards the outlet 116. However, as the valve member 245 is raisedupwards (according to the orientation shown), the diameter of the valvemember 245 proximate the lower bore 347 decreases to a minimum diameter,D₂. As the diameter proximate the lower bore 347 decreases, a spacebetween the valve member 245 and the lower bore 347 is created to allowfluid to flow from the inlet 115 towards the outlet 116. As can beappreciated, when the entire valve member 245 is above the lower bore347, a maximum flow can be achieved. However, while at least a portionof the valve member 245 remains within a portion of the lower bore 347,proportional flow control can be achieved.

Although the tight tolerances between the bores 347, 348 and the valvemember 245 are designed to provide a substantially fluid tight sealing,at higher pressures, some fluid is likely to leak past the substantiallyfluid-tight seal and thus, the valve module 114 includes a fluid returnport 350. The fluid return port 350 is positioned between the bushing346 and the biasing member 244. The fluid return port 350 may be influid communication with the fluid supply 104, for example. While themaximum diameter D₁ of the valve member 245 maintains a substantiallyfluid tight seal with the upper bore 348, in the event that fluid flowspast the valve member/upper bore interface, the fluid will simply bediverted back to the fluid supply 104 at a substantially reducedpressure via the fluid return port 350. A sealing member 351 can alsoprevent fluid from flowing past the fluid return port 350 towards thebiasing member 244. According to an embodiment, the sealing member 351may comprise an elastomer sealing member, for example. However, othertypes of sealing members may be used.

The features described above for the valve module 114 allow for preciseand proportional control of high-pressure liquids. In addition to thevalve module 114, the waste heat recovery system 100 also needs to beable to adequately control the flow of superheated vapor.

FIG. 4 shows a cross-sectional view of the vapor control module 103according to an embodiment. According to an embodiment, the vaporcontrol module 103 comprises a housing 403, which houses the bypassvalve 128. As shown, the bypass valve 128 can include a biasing member460, which can bias a valve member 461 towards a first position. In thefirst position illustrated in FIG. 4, the valve member 461 can open afluid communication path between the inlet port 127 and the first outletport 157 and close a fluid communication path between the inlet port 127and the second outlet port 158. According to an embodiment, between theinlet port 127 and the outlet port 157 is a needle valve 131. The needlevalve 131 can be provided to control the flow rate and pressure throughthe vapor control module 103. According to an embodiment, the needlevalve 131 can be adjusted by actuating the adjustor 431. As shown, whenthe bypass valve 128 is in the first position, fluid can flow from theinlet port 127, through the needle valve 131 to a bypass fluid chamber462. According to an embodiment, the valve member 461 includes a valveseal 463, which is located within the bypass fluid chamber 462 and isconfigured to seal against a valve seat 464. However, when the bypassvalve 128 is actuated to the first position, the valve seal 463 is movedaway from the valve seat 464.

According to an embodiment, downstream from the bypass fluid chamber462, the superheated fluid flows into the venturi 132. The venturi 132can further reduce the pressure of the superheated fluid and increasethe velocity of the superheated fluid before exiting the second outletport 157 and flowing to the condenser 134. In some embodiments, thesuperheated fluid may increase to a sonic velocity, for example. Asdiscussed above, in some embodiments, the vapor control module 103 canfurther include an injection port 465, which can receive cooling fluidfrom the fluid supply 104 via the de-superheat control valve 133. Whenvalve 133 is actuated, the cooling liquid can flow into the vaporcontrol module 103 at the venturi 132 of the bypass circuit 130. Asthose skilled in the art can appreciate, by increasing the velocity ofthe superheated fluid to sonic velocity, the cooling liquid is betterdispersed and therefore, the cooling efficiency is increased. Therefore,prior to the fluid leaving the outlet port 157, the superheated fluid iscooled. This feature helps reduce the thermal shock experienced by thecondenser 134.

Additionally or alternatively, a flow control valve 142 may regulate theflow of the fluid from the de-superheat control valve 133 to theinjection port 465. The flow control valve 142 may control the flowbased on parameters in the waste heat recovery system 100 and/or theengine 101. For example, a temperature gauge 144 may provide atemperature of fluid in the bypass circuit 130. The flow control valve142 may control the flow of the fluid to the injection port based on thetemperature of the fluid in the bypass circuit 130. The flow controlvalve 142 may also control the flow based on the engine's 101 poweroutput. For example, the flow control valve 142 may increase the flow tothe bypass circuit 130 when the engine's 101 power output drops due tothe vehicle slowing due to the operator releasing the gas pedal. Thecooling fluid may enter the bypass circuit 130 to cool the superheatedfluid when the vapor control module 103 diverts the superheated fluidflow from the expander 129 to the bypass circuit 130.

According to an embodiment, the bypass valve 128 can also be actuated toa second position. In the second position, fluid flows from the inletport 127 to the second outlet port 158 towards the expander 129. Inorder to actuate the bypass valve 128 to the second position, the pilotsupply valve 137 can be actuated from the default, first position, to asecond position. Substantially simultaneously, or prior to actuating thepilot supply valve 137, the exhaust valve 138 can also be actuated to asecond position to close the exhaust valve 138. As can be appreciated,in alternative embodiments, the pilot supply valve 137 and the exhaustvalve 138 can be replaced with a single 3/2-way valve or some othersingle valve configuration. With the exhaust valve 138 closed and thepilot supply valve 137 actuated, fluid pressure is supplied to the pilotvalve actuator 139. As can be seen in FIG. 4, pressurized fluid suppliedto the pilot valve actuator 139 acts on a piston member 439. When thepressure acting on the piston member 439 reaches a threshold pressure,the biasing force of the biasing member 460 and the fluid pressureacting on the valve member 461 is overcome to move the valve member 461towards a second position (down according to the orientation shown). Asthe valve member 461 moves down, the valve seal 463 seals against thevalve seat 464 and a second valve seal 466 unseats from a second valveseat 467.

According to an embodiment, with the valve member 461 in the secondposition, fluid can flow from the inlet port 127 towards the secondoutlet port 158 and towards the expander 129. However, with the valveseal 463 sealed against the valve seat 464, fluid is substantiallyprevented from flowing directly to the condenser 134. Although the valveseal 463 ideally forms a completely fluid-tight seal, even if a smallamount of fluid escapes past the valve seal 463, the fluid will simplyflow to the condenser 134 and thus, a pressure will not build up in thebypass fluid chamber 462.

As can be appreciated, the vapor control module 103 must be able towithstand the extreme pressures and temperatures of the superheatedvapor flowing from the evaporators 120, 121. Therefore, a number offeatures are included in the vapor control module 103 to accommodatesuch extreme conditions. According to an embodiment, the sealingperformed by the bypass valve 128 can be accomplished withmetal-to-metal sealing. Therefore, the valve seals 463 and 466 alongwith the valve seats 464, 467 can all comprise a metal. Those skilled inthe art will readily appreciate suitable metals. Furthermore, because ofthe poppet nature of the valve seals 463, 466 and valve seats 464, 467,little pressure drop is experienced through the bypass valve 128 when inthe second position.

Additionally, the pilot valve actuator 139 is designed to limit the heattransferred to the elastomeric seal 468 and guide ring 469 used for thepiston 439. For example, according to an embodiment, the pilot valveactuator 139 can include a plurality of heat fins 470. As is generallyknown in the art, heat fins can aid in dissipating heat by increasingthe surface area of the component. Therefore, the heat fins 470 canremove some of the heat experienced by the contact between the housing403 and the pilot valve actuator 139. In addition to the heat fins 470,according to an embodiment, the pilot valve actuator 139 can be coupledto the housing 403 using brackets 471. The brackets 471 can create anair gap 472 to further increase the surface area of the pilot valveactuator 139. This minimizes the surface area of contact between thepilot valve actuator 139 and the housing 403. These features can help tothermally decouple the pilot valve actuator 139 from the remainder ofthe vapor control module 103.

With an understanding of the liquid control module 102 and the vaporcontrol module 103, attention is now drawn to the operation of the wasteheat recovery system 100.

According to an embodiment, the waste heat recovery system 100 can beused by motor vehicles that include IC engines, such as the IC enginedepicted by block 101 in FIG. 1. The waste heat recovery system 100 canbe controlled by the motor vehicle's electronics control and thus, maynot include its own separate electronics. However, in other embodiments,a separate waste heat recovery system electronics may be utilized.

According to an embodiment, in a default position, the system drainvalve 113 is opened to allow fluid to drain from the liquid controlmodule 102. As mentioned above, this may be desired when the engine isturned off, when energy is not required by the expander 129, or anyother time that is desired by the user. When the system drain valve 113is opened, pressurized fluid is substantially diverted from the valvemodule 114. However, when the system drain valve is actuated and closed,fluid is substantially prevented from exhausting from the liquid controlmodule 102. The high-pressure pump 105 pumps fluid from the fluid supply104 to the liquid control module 102. According to an embodiment, one ofthe first or second liquid control valves 118, 119 can be opened whilethe other is closed. Therefore, fluid can be supplied to one or more ofthe two or more evaporators 120, 121. According to the embodiment shownin the figures, the first liquid control valve 118 is opened to supplyfluid to the first evaporator 120 while the second liquid control valve119 is closed and thus, no fluid is supplied to the second evaporator121.

In the embodiment shown, in a default position, the pilot supply valve137 is also biased to a first position to prevent fluid communicationbetween the fluid supply 104 and the pilot valve actuator 139 while theexhaust valve 138 is default to a first position to exhaust any fluidthat is acting on the pilot valve actuator 139. With the pilot supplyvalve 137 and the exhaust valve 138 biased to their first positions, thebypass valve 128 provides a fluid communication path between the two ormore evaporators 120, 121 and the condenser 134 via the bypass circuit130. According to an embodiment, the de-superheat control valve 133 maybe biased towards a first position where fluid from the fluid supply 104is not provided to the injection port 465. However, once a thresholdtemperature is measured by the temperature sensors 124 and/or 144, thede-superheat control valve 133 can be actuated to provide cooling fluidto the injection port 465 to de-superheat the fluid prior to reachingthe condenser 134. It should be appreciated that when the fluid comingfrom the evaporators 120, 121 is at a temperature below the thresholdtemperature, the cooling fluid may not be needed. This may occur whenthe engine 101 is initially started and has not warmed up to anoperating temperature, for example.

According to an embodiment, the bypass valve 128 may remain in thedefault bypass mode when power is not needed from the expander 129 orwhen the temperature of the fluid has not reached the thresholdtemperature, for example. Power may not be needed from the expander 129when the vehicle is braking or stopped. Therefore, in some embodiments,a brake signal may automatically de-actuate the pilot supply valve 137and the exhaust valve 138 to allow the biasing member 460 to actuate thebypass valve 128 to the default bypass mode.

According to an embodiment, once additional power is needed or desiredfrom the expander 129, the pilot supply valve 137 and the exhaust valve138 can be actuated from their first position to their second position.In their second position, fluid from the fluid supply 104 can besupplied to the pilot valve actuator 139 to actuate the bypass valve 128to its second position to provide a fluid communication path between thetwo or more evaporators 120, 121 and the expander 129. It should beappreciated that while the pilot fluid applied to the pilot valveactuator 139 may come from a separate fluid supply (not shown), by usingthe fluid supply 104 as the pilot actuating fluid, leakage issues areminimized. Furthermore, it should be appreciated that in otherembodiments, the bypass valve 128 may be actuated using other knownmethods such as solenoids, piezo-electric actuators, stepper motors,etc. In some embodiments, the bypass valve 128 may also beproportionally controlled. Therefore, the bypass valve 128 should not belimited to pilot actuated valves.

According to an embodiment, with the bypass valve 128 actuated to thesecond position, the fluid coming from one or more of the two or moreevaporators 120, 121 can be delivered to the expander 129 where thefluid's energy can be converted to mechanical energy. Therefore, theexpander 129 allows some of the waste heat from the engine 101 to beconverted back to useful energy. As shown, the fluid can leave theexpander 129 and flow to the condenser 134 and eventually back to thefluid supply 104. Those skilled in the art can readily appreciate thatwhen the bypass valve 128 is actuated to the second position to supplysuperheated vapor to the expander 129, the cooling liquid is not neededat the injection port 465 and thus, the de-superheat control valve 133can be de-actuated to the default position.

As can be appreciated, when power is required at the expander 129, theliquid control valves 118, 119 can be proportionally controlled toachieve the desired pressure and temperature of the fluid leaving thetwo or more evaporators 120, 121 and flowing into the vapor controlmodule 103. The liquid control valves 118, 119 can be controlled basedon operating temperatures of the two or more evaporators 120, 121, forexample.

The embodiments described above provide an efficient waste heat recoverysystem 100 that can draw heat from two or more evaporators 120, 121 in aproportional manner. According to an embodiment, the flow of fluidvapour from the evaporators 120, 121 can be controlled using liquid fromthe same fluid supply that delivers fluid to the evaporators 120, 121.Consequently, a separate pilot pressure is not required. Further, fluidfrom the fluid supply 104 can be used to de-superheat the fluid exitingthe vapor control module 103 during a bypass mode. Another advantage ofthe waste heat recovery system 100 of the present embodiment is that theliquid control valves 118, 119 as well as the bypass valve 128 utilizemetal-to-metal sealing, which can withstand higher pressures andtemperatures without failing.

The detailed descriptions of the above embodiments are not exhaustivedescriptions of all embodiments contemplated by the inventors to bewithin the scope of the present description. Indeed, persons skilled inthe art will recognize that certain elements of the above-describedembodiments may variously be combined or eliminated to create furtherembodiments, and such further embodiments fall within the scope andteachings of the present description. It will also be apparent to thoseof ordinary skill in the art that the above-described embodiments may becombined in whole or in part to create additional embodiments within thescope and teachings of the present description.

Thus, although specific embodiments are described herein forillustrative purposes, various equivalent modifications are possiblewithin the scope of the present description, as those skilled in therelevant art will recognize. The teachings provided herein can beapplied to other waste heat recovery systems, and not just to theembodiments described above and shown in the accompanying figures.Accordingly, the scope of the embodiments described above should bedetermined from the following claims.

We claim:
 1. A waste heat recovery system (100) for an engine (101),comprising: a fluid supply (104); one or more evaporators (120, 121)adapted to transfer waste heat from the engine (101) to fluid from thefluid supply (104) to heat the fluid to a superheated vapor; a condenser(134); a bypass circuit (130) in fluid communication with an outlet onthe one or more evaporators (120, 121) and an inlet on the condenser(134); and an injection port (465) in fluid communication with the fluidsupply (104) and the bypass circuit (130) and adapted to inject fluidfrom the fluid supply (104) into the bypass circuit (130) to cool thesuperheated vapor in the bypass circuit (130).
 2. The waste heatrecovery system of claim 1, the system being adapted to inject fluidinto the bypass circuit based on one or more parameters in the wasteheat recovery system (100) or the engine (101).
 3. The waste heatrecovery system of claim 2, wherein a parameter is a temperature in thewaste heat recovery system (100).
 4. The waste heat recovery system ofclaim 2, wherein a parameter is a power output of the engine (101). 5.The waste heat recovery system of claim 2, wherein the system comprisesa vapour control module adapted to control flow through the bypasscircuit, wherein a parameter is a parameter of the vapor control module(103).
 6. A waste heat recovery system (100) for an engine, comprising:a fluid supply (104); one or more evaporators (120, 121) in fluidcommunication with the fluid supply (104) and receiving waste heat fromthe engine (101); a bypass valve (128) including: an inlet port (127) influid communication with an outlet of the one or more evaporators (120,121); a first outlet port (158) in fluid communication with an expander(129); and a second outlet port (157) in fluid communication with acondenser (134), wherein the second outlet port (157) includes aninjection port (465) in fluid communication with the fluid supply (104).7. The waste heat recovery system (100) of claim 6, further comprising:two or more evaporators (120, 121) positioned in parallel to oneanother; and a valve module (114) including an inlet port (115) in fluidcommunication with the fluid supply (104), a first outlet port (116) influid communication with a first evaporator (120) of the two or moreevaporators (120, 121), and a second outlet port (117) in fluidcommunication with a second evaporator (121) of the two or moreevaporators (120, 121) for selectively providing a fluid communicationpath between the fluid supply (104) and one or more of the two or moreevaporators (120, 121).
 8. The waste heat recovery system (100) of claim7, wherein the valve module (114) comprises a first liquid control valve(118) selectively providing a fluid communication path between the fluidsupply (104) and the first evaporator (120) and a second liquid controlvalve (119) selectively providing a fluid communication path between thefluid supply (104) and the second evaporator (121).
 9. The waste heatrecovery system (100) of claim 8, wherein the first and second liquidcontrol valves (118, 119) comprise proportional valves.
 10. The wasteheat recovery system (100) of claim 8, wherein the first and secondliquid control valves (118, 119) comprise proportional needle valves.11. The waste heat recovery system (100) of claim 10, further comprisingone or more bushings (346) positioned within a housing (214) of thevalve module (114) and forming a substantially fluid-tight seal with avalve member (245) of the proportional needle valve.
 12. The waste heatrecovery system (100) of claim 11, wherein the valve member (245)comprises a tapered needle having a maximum diameter (D₁), which tapersdown to a minimum diameter (D₂).
 13. The waste heat recovery system(100) of claim 11, further comprising an elastomer sealing member (351)forming a substantially fluid-tight seal between the valve member (245)and the housing (214) outside of the substantially fluid-tight sealbetween the valve member (245) and the one or more bushings (346). 14.The waste heat recovery system (100) of claim 7, further comprising apressure control valve (110) in parallel with the valve module (114).15. The waste heat recovery system (100) of claim 6, wherein the bypassvalve (128) comprises a pilot valve actuator (139) for actuating thebypass valve (128) from a first position to a second position.
 16. Thewaste heat recovery system (100) of claim 15, wherein the pilot valveactuator (139) is selectively in fluid communication with the fluidsupply (104) via a pilot supply valve (137).
 17. The waste heat recoverysystem (100) of claim 6, further comprising an injection port (465) influid communication with the second fluid port (157) and selectively influid communication with the fluid supply (104) via a control valve(133).
 18. The waste heat recovery system (100) of claim 17, furthercomprising a venturi (132) positioned in the second fluid port (157).19. A method of recovering waste heat from an engine with a waste heatrecovery system, comprising: generating superheated vapor with one ormore evaporators with the waste heat from the engine; and cooling thesuperheated vapor with fluid from a fluid supply based on one or moreparameters in the waste heat recovery system or the engine.
 20. Themethod of claim 19, wherein a parameter is a temperature in the wasteheat recovery system.
 21. The method of claim 19, wherein a parameter isa power output of the engine.
 22. The method of claim 19, wherein aparameter is a parameter of a vapor control module adapted to controlflow through a bypass circuit.
 23. The method of claim 19, wherein aparameter is a pressure in the waste heat recovery system.
 24. A wasteheat recovery system (100) for an engine (101), comprising: one or moreevaporators (120, 121) adapted to transfer waste heat from the engine(101) to fluid from a fluid supply (104) wherein the engine (101)generates the waste heat with the fluid.
 25. A waste heat recoverysystem according to claim 24, wherein the engine (101) is in fluidcommunication with the fluid supply (104).
 26. A waste heat recoverysystem according to claim 24, wherein the fluid supply (104) comprises afuel tank for the engine (101).
 27. A waste heat recovery systemaccording to claim 24, wherein the fluid comprises fuel for the engine(101).
 28. A method of recovering waste heat from an engine, comprising:generating the waste heat with the engine from fluid from a fluidsupply; and transferring waste heat from the engine to fluid from thefluid supply with one or more evaporators.
 29. The method of claim 28wherein the fluid is a fuel for the engine.